250 
MR. W. K. PARKER ON THE STRUCTURE AND 
“ Challenger ” expedition, and put into my hands by John Murray, Esq.; and 
one dry skull of the same species; locality unknown.* 
Stage 1 , a. — The embryo of Galeopitliecus volans ; 5^ inches long. 
The figures given of this embryo (Plate 16, figs. 15, 15a) at once show its utter 
unlikeness to the normal Insectivora ; it belongs, undoubtedly, to their level or plat¬ 
form, but its relation to them is doubtful in the extreme. To the group below—the 
Marsupials—it is related, and to a group above—the Chiroptera—it is also related, 
as I shall show anon. 
I shall not enter into either the zoological characters, or the visceral anatomy of 
this type, but speak of what I have found in the developing skull. Biologists can 
then deal with the evidence as to the Insectivorous or Chiropterous nature of this very 
archaic beast, at their leisure. 
Stage 1 (a).— Shull of Galeojfithecus volans ; embryo, 5-| inches long. 
a.—Investing bones. 
The general appearance of the dissected skull, with the investing bones complete 
upon it (Plate 37, figs. 1, 2; and Plate 38, fig. 1) is very similar to that of a young 
Phalanger, or Cuscus, of the same size, but about three months old,t but the form is 
in reality intermediate between that of the skull of those Metatherian types, and that 
of the young Pteropus, or Frugivorous Bat. By keeping these comparisons in mind 
we shall be able to see the meaning of many things in this type, which, however, has 
some unique characters ; these are strange and unique, because the kindred of the two 
Colugos are all extinct. This skull is very flat or depressed, and its great breadth 
across the middle gives it an almost oval outline ; the short snout scarcely breaking 
such a supposed circumscribing line, and the occipital region being merely siuuous, 
instead of regularly arcuate. The roof (Plate 37, fig. 2, upper vieiv) is mainly com¬ 
posed of three pairs of bones that form a very regular series ; these are the nasals, 
frontals, and parietals («., f, pi), and behind these is the single interparietal {ip.), 
once, no doubt, composed of a pair of centres. The nasals (n.), flanked by the 
maxillaries and premaxillaries (mx., px. ), are as long as the parietals, and nearly as 
long as the frontals. They are pointed in front and very broad behind, stretching out¬ 
wards so as to be sutured to most of the fore margin of the frontals. Here, at once, 
we see the effect of the general depression of this peculiar skull, almost unique in the 
class, in its flatness and breadth. The frontals are well formed, and from the lachry¬ 
mal to the parietal grow outwards as a neat supra-postorbital ledge ; a large supra- 
* The large size of the embryo which had, apparently, been taken from the uterus—as there was no 
shrinking whatever of the umbilicus—and the remarkable differences, soon to be described, between it 
and the other kinds, satisfy me that this belongs to the large species, Galeopitliecus volans. 
t At birth the Australian Marsupials range from the size of a new-born Mouse to that of a new-born 
Rat; this larger size is what is attained by Macropus major. 
